Mechanical brake / Castle Neu problem
 

Hi all,

Having given the truggy a bash with the motor brakes on a few different settings, as well as a few different pinions, I have decided to go back to mechanical brakes.

I've now run into a problem. With the old feigao motor, the smallest pinion I could use was the 14T. I had to grind down the brake pad holders on the rear brakes a little in order to get it to fit, but it worked fine, although I normally ran with the 15T pinion.

I tested the 15T pinion with the motor brakes and the performance and amp draw was perfect, so I want to use mech brakes with that. Unfortunately the CC Neu motor is a slightly larger diameter than the Feigao.

The largest pinion I have is a 17T and it barely touches the spur lol. I could grind down the fins and get it closer, but from the looks of things, it wouldn't be close enough.

Anyone got any tricks to get it to fit, or do I need to resign myself to motor brakes?

Also, I've got a Medusa 80mm coming, which should be the same 36mm diameter as the Feigao which should fit perfectly with the larger pinions, but that's if it ever gets here. Can anyone with a 80mm medusa confirm that they are actually no larger than 36mm diameter?

thanks

RC Monster sells a "Front Motor Cover or brake spacer". Select the brake spacer from the drop down.

This is the best solution for this issue.

Another way is to use a motor with a lower kv so you can run a bigger pinion. If you don't have another motor, then the $10 brake spacer is the way to go.

What an excellent idea! I saw those, but I thought they were only for Neu motors.

I don't suppose anyone has a picture of an RCM brake spacer? I was considering something like that but didn't know Mike sells em. I'm also not sure if it would solve the issue unless its fairly wide. It may allow the front brake pad fit, but the rear one would still be stuck flush up against the side of the can. .25" = about 6mm so it might work, but as they say, a picture says 1000 words.

The 80mm medusa coming is the 1600kv one, so the larger pinion will be fine for that, just want to get something that works until whenever they eventually ship mine out.

cdis,
i have had this same problem. you have two options. get a tekno kit or make/buy a spacer. i made my own by using CA to glue to pices of 3mm carbon together. it was just the right thickness. here are some pics. if you have 1/4" carbon or alum laying around just use that. drill your screw/shaft holes, and then cut the piece the same diameter as your motor can and grind down one side so it looks like a 3/4 moon. then countersink the two holes that wont be used to mount the motor. this way you can use a flat head screw to hold the piece to the motor and the the other 2 holes to mount up. depending on your mesh you might only be able to use one screw to hold the piece to your motor. in these pics i have two but i ended up having to use only one screw with a 13t pinion. good luck. and yes RCM sells something almost identical out of alum for like $12 i think. you will have to search the site though. its not the black alum Neu endbell cover but its a silver alum 1/4" thick oblong shaped thing.
oh, and one other thing. you will most likely need a Tekno long shank pinion to reach the spur now. thats what i had to do. because the motor now sits further back from the spur a regular pinion wont reach. have fun!:wink:


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The RCM spacer is an aluminum version of Ryu James's CF spacer but one side is a crecent moon shape to make space for the brake disk/calipers.

http://www.rc-monster.com/proddetail...rontmotorcover

Select the .25" brake spacer from the drop down.

The RCM spacer is the best design available (in my opinion) as the spacer mounts to all four motor mounting holes and uses two seperate mount holes (the RCM mount has six holes total) to mount the motor which eliminates any potential winding damage caused by long screws. The only thing I see that would make this a better design would be to add space in the center of the spacer to fit a 5x10 or 5x11mm bearing to increase the rigidity of the motor shaft as the pinion must sit .25'" farther out on the shaft. This additional bearing should eliminate addition stress and wear to the existing motor bearings. You can also drill out a hole to fit a bearing yourself as well. With that said, I have used the RCM spacer for months and have not noticed any ill affects. The Castle NEU motor shaft should be long enough to fit a pinion without the need of a long shank pinion but as for other motors out there, they will most likely need a long shank pinion.

Ryu James,
I also wanted to commend you on the work you've done on your RC8T. It looks very nice.

I took a look at your other pics and since we're discussing brakes I thought I throw out my 2 cents. I see you are using a full size servo for both front and rear brakes and was wondering if you have considered using a hybrid configuration of both motor brakes and mechanical brakes.

I have installed a mini servo (such as the crt.5 servo) to only activate the rear mechanical brakes while utilizing minimal motor braking power for brake bias. I've found that using rear mech brakes along with ~10% to 15% motor brakes provides a very nice bias. Small steps in motor brake power is all you need to find the right amount of bias. This configuration also reduces the amount of power needed from a brake servo so you will not need such a large/heavy servo. The size and weight savings of this setup may be something to consider in the future.

Thanks for the help boys.
Hopefully the new Medusa will have a long enough shaft. Ordered a spacer just now but I think I might have to dodge something up before it gets here lol :D

thanks Star,
i have some carbon at the machine shop right now being CNC'd. i am making a carbon chassis for the RC8t, 8ight-T, and MBX5T with kickup. if the prototypes survive my severe testing i am going to produce them. my website is modifiedrc.com and will be up soon. these chassis' are going to be sick and i am talking with some highly-respected companies in hopes of being able to sell these as a complete conversion kit. my goal is to not compete with other companies out there but work with them and provide a means for everyone to be involved to make a little money but more importantly to just have fun and provide a kit that is not yet available to the 1/8 brushless customer. it will be more expensive than the normal conversion kits obviously due to the carbon fiber but i think there are a few people out there that this product will cater to. myself being one of them. if the venture doesnt work out i still get custom carbon 1/8 truggies for myself which is what this started out as anyway.

so as far as the brake thing that is a good idea. i will have to try the micro server. i actually have my esc set to 15% brakes with my current setup, to kind of act like down-shifting when i brake. i really like my setup but i do have my bias set more to rear so doing the rear/hybrid setup might work. just wondering though, do you have to use a bunch of spacers to get the micro server to be tall enough to be the right heighth for the center diff? i hate using spacers to achieve optimal setup. monster Mike told me about also making your own center diff top plate to extend out and mount the micro server in that. that is an option i guess. for now i will probably stick with what i have as that is how my chassis are being made. plus, the carbon chassis will save me more weight than switching to a micro server will. thanks for the tip though. i am sure i will try it out in the near future on another project or something.

Why? The RCM shipping is so fast...

Yes, the medusa 36MM is the same. Fit perfect for me.

I'm in Brisbane, Australia, so shipping takes a little longer :(

I made my own mount from a crt.5 radio tray which is mounted to the top of the center diff so there are no spacers involved.

You'll probably appreciate the mount as it's CF :intello:
pics in my thread here: http://www.rc-monster.com/forum/showthread.php?t=18076

The custom CF top plate would be the best way to go and is actually what I will most likely end up doing. I just have to gets some CF. Its not the cheapest material but it works and looks good.

so is that i micro server for your brake, Star? i cant tell in the pic. and is the carbon mounted to the center diff or the chassis?

It's a hitec digital mini. I cheated and used some alum to mount the CF to the motor mount. I have a CF top plate on my mugen but the holes don't line up quite right so I got to get another piece of CF and replace the whole RC8T top plate like you mentioned.

Once again, awesome shipping from Mike. Ordered on the 16th (was the 17th here), and the spacer arrived this morning! :D Thanks Mike!

So, now the bad news lol, the spacer doesn't "space" enough lol. Lametastic! :(

I am attempting to use a 15T pinion, but it's about 1-1.5mm too far out to mesh properly, with the spacer on. The 17T is almost there, but not quite, and the 18T is almost perfect.

The spacer has improved but not fixed the issue. Without the spacer, the brake pads/screw were hitting the raised fins on the motor, so the pinion was even further away, so far that even the 18T pinion wouldn't mesh.

With the spacer, I can at least get the 18T to mesh (its probably a tiny bit too far out but I can live with that).

Anyway, the issue is that the 2200kv motor is like crazy over geared with the 17T pinion, so I can't imagine how crazy the 18T would be. The 15T is MUCH nicer, more controlable, and the amp draw and battery life is excellent, unfortunately, I can't get it to fit with the mech brakes.

So, is there anything I can do to make it fit. I assume I'd have to make a thinner spacer to add to the RCM one, like out of 3mm Aluminum or something like that, or perhaps cut some material away from the end of the can?

Here's a photo
http://i157.photobucket.com/albums/t...IMG_1988_2.jpg

yeah, that sucks bro. frustrating huh. you can cut into the endbell but i wouldnt. i did this and once you start it never stops and your motor looks like crap. plus you usually have to cut away way more than you had anticipated. i would get a another piece of 3mm alum or carbon and make the spacer thicker......or buy a tekno conversion kit.....at least that is what i would do next time if you plan to run mechanical brakes. Mike sells the kits on his site or you can get them from impaktrc.com. good luck.

3mm isn't much
An easy solution to this is to run slightly bigger gears.
What vehicle are you using. What is the current pinion spur? 46/15?
it sounds like 48/16 would fix you up.

You can always run your 17T pinion and set your throttle end point down to 85 or 90% until you get new gears or make a small spacer.

cdis,
i was going to suggest that you get a larger spur instead of just trying to make it work with a larger pinion. just take what your ideal gearing is and divide the 2 numbers to get the gear ratio. for example 15/48 is ratio of 3.2 so if you need to go to 50t spur then figure what pinion will get you close to the same ratio and your setup will be very close to what you wanted in the first place. eg. a 16/50 ratio is 3.12. just go up in spur size and this will require a larger pinion also and the result will be a mesh that works with your current spacer. if you already have a 54t spur on then i dont know what to tell you. i havent seen mod1 gears much larger than that.....although i am sure you could find one somewhere.

Yea it is a bit frustrating.

I agree starscreem, 3mm isn't much, but it should be just enough to allow the brake pads to clear the front of the motor. 3mm Alu is just what I have on hand. The problem would be to make up something as accurately as Mike has done for the brake spacer.

The car is a Kyosho ST-RR. It's running the stock 50T spur gear at the moment. I was thinking about getting a bigger spur gear, but no one in Australia carries parts for the ST-RR yet... Should a got an RC8T lol.

Anyway, yea, if I could, I would run a bigger pinion and maybe the 16 or 17t pinion, whichever one fits best.

This is only an issue until the Medusa arrives. I've ordered the 1600kv motor, so I'm hoping that I'll be able to use the 17T pinion with 7s1p A123 and get some decent amp draw and run times.

Thanks Ryu, I didn't know that formula for working out the gear ratio :D

From your picture, it looks like you could go with a smaller brake disc. The smallest disc I know if is the Losi 8ight rear brake disc. A smaller diameter disc my give you the extra 3mm you need.

A smaller diameter brake disk wouldn't help would it? What would be more helpful would be either thinner brake pads? Then the motor would fit "over" the top of the end of the screw that holds the brake pads together, which you can see is touching the front of the motor, and hindering it from moving any further toward the spur.

Righto, so I decided to bulk up the RCM spacer a little to use with my CC NEU until the medusa arrives.

It's pretty rough looking, but it works - can pinions as small as 12T.

http://i157.photobucket.com/albums/t...R/IMG_2046.jpg

I wouldn't cut the can...it will surely void your warrantee if not mistaken. Another smaller spacer may be in order or have Mike make you a new one that is a tad wider.

Haha yea no way I was going to cut the can. Those little bits of Alu work fine and there's no play in the mounting, so I'll live with that until the Medusa arrives.

The CC Neu is insane on 7s1p A123s and 12T pinion! :D

Motor Temp/gearing
 

Hello again everyone :D

I have a question regarding the gearing on my setup now. Im currently running the 12t pinion with the stock 50T spur, which performance wise is working perfectly. Similar, but faster to my nitro car, and no crazy wheel ballooning etc.

I measured the temp of everything after my last run, and found that my motor was fairly hot when compared to the ESC and batts.

The ESC was about 30C, the batts were 33C but the motor was just under 50C (degrees in Celsius).

I looked up the thread on motor/speed/batt temps which has

Hot motor, cool controller, cool batteries = undergeared
Cool motor, hot controller, hot batteries = overgeared

So I guess my setup is currently under geared. Does that mean I need to go up a couple of pinion sizes to "gear up", or does it mean that I need to go down a few?

Thanks guys :D

That is correct. To gear up, you can either get a pinion gear with more teeth, or a spur gear with less teeth. Both will have the same effect.

Hmm, that's a bit sad, as my run times were awesome with the 12t lol. Thanks for the quick answer tho, I'll try the 13-15t pinions and see how I go.

I just wish my 1600kv medusa would arrive already! 2200kv is way overkill for 7s a123s lol

50C is about the coolest temps you can get on any motor after a run. There is nothing to be concerned about until you exceed 175F or about 80C.